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The 2014 Farmers Almanac
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What Is a Microburst?

What Is a Microburst?

Sometimes the smallest things can be the most destructive. Consider the termite. Though tiny in size, these insects can cause hundreds on thousands of dollars in damage before anyone even knows they’re there.

Viruses are literally microscopic. Invisible to the naked eye, they spread on the wind, sickening, or even killing, people who never even saw them coming. And everyone knows the sharpest knives are those with the thinnest edges.

This principle also applies to storms. Consider “microburst.” The name sounds like something you might call a short-lived rainstorm, as in “I thought it was going to pour all day, but luckily it was just a microburst.”

If you’ve ever had the misfortune to live through a microburst, though, you’ll know there’s nothing lucky about it.
This type of storm takes its name from the fact that they are very localized and short-lived, affecting an area of 2.5 miles or less and lasting anywhere from a just few seconds to 10-15 minutes, at the most.

What microbursts lack in size and longevity, though, they more than make up for in intensity. A single microburst can create winds speeds up to 100 miles per hour and cause damage as severe as an F1 tornado, downing trees and damaging structures.

Unlike tornadoes, though, microbursts are not cyclonic and they stay in one place. Microbursts are caused by downdrafts within a thunderstorm.  During a storm, air and water droplets become suspended in an updraft high up in the clouds. The stronger the updraft is, the higher the moisture and air are push, and the colder they become. As the air and water cool, they become heavier, until eventually the storm system is unable to support that heavy core. When that happens, all of that water and air begin to sink, plummeting toward the Earth at a rapid speed.

As the downdraft makes landfall, it spreads outward, leaving behind a path of destruction that radiates out from its initial contact point.  From the ground, microburst damage can be difficult to distinguish from tornado damage. From the air, though, the two kinds of storms each leave behind their own calling card.

For instance, tornadoes leave trees scattered around in haphazard directions, whereas a microburst pushes trees outward in straight lines, diverging from a single point.

Microbursts come on very suddenly and can be hard to predict, making them especially dangerous for aircraft. Several fatal plane crashes having been blamed on microbursts.

The term microburst was coined by Ted Fujita, the Japanese-American meteorologist who was instrumental in creating the tornado intensity scale that bears his name.

Downbursts occur in three stages: the contact stage, the outburst stage, and the cushion stage.
As the name suggests, the contact stage is when the sinking air makes its initial contact with the ground. The highest winds and most damage occur during this stage.

During the outburst stage, air from the downburst moves outward from the point of impact, curling along the leading edge. Finally, during the cushion stage, the winds at the contact point begin to weaken, while the wind moving outward continues to accelerate.

Eventually though, friction slows the winds down, and the microburst dies out as quickly as it come on.

Unfortunately for those on the ground, cleaning up after a microburst takes much longer than the storm itself.

5 comments

1 Michael Amato { 07.16.14 at 9:31 pm }

While storm chasing several years ago, my friend Don & I actually watched a microburst a few miles from where we were. It lasted about 30 seconds and as it hit a dirt field, We could see the dust being kicked up by the microburst. That was the only microburst I ever observed.

2 Barbara LaHart { 07.16.14 at 12:57 pm }

we had one about five years ago . we lost 29 trees including all our apple trees which were heavy with fruit. in the area effected thousand of trees were knocked over or broken the weather service said because our small/new apple trees were knocked over and broken the believe the wind was well over 100 mph. to this day on golf course next to us there are still trees being cleaned up. and still pieces of the neighbors roof driven into the siding on our garage. it only lasted a minute. there was a big roar my husband and i both said at the same time what the h-ll is that. trees were on houses and cars the power was out for 5 days .

3 Ira { 07.16.14 at 10:10 am }

Had one last thursday. Still cleaning up after 5 days! Cost ? very expensive.

4 Sandrita { 07.16.14 at 9:44 am }

My thing to learn for the day. I swear a microburst visited neighborhood last week. Leaves and branches all over the place but no tornado report.

5 D Starook { 07.16.14 at 9:17 am }

Very interesting. I’ve allways wondered how these work since seeing the smoke from the downed Airliner at DFW in the 90’s.

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